Sigma-delta (ΣΔ) analog to digital converters, also referred to as Delta-Sigma analog to digital converters are widely used in audio applications such as smart amplifier, digital and analog microphones, power integrated circuits and instrumentation. Such applications may require high dynamic range to adapt to significant differences in input signal level. High gain may be needed for a small input voltage whereas for larger voltages, the gain must be reduced to avoid saturation of the ADC. To overcome this a programmable gain amplifier (PGA) may be used before the input of the ADC to vary the gain.